It shall be the duty of each elected and appointed assessor and assistant township and triennial assessor to produce to the commissioners, or board of revision of taxes, or board for the assessment and revision of taxes, of the county, within twenty days after his election or appointment, a copy of the oath or affirmation taken and subscribed by him as is hereinbefore directed, and attested by the person before whom the same was administered, which shall be filed by the commissioners, or said boards, in their respective office.
72 P.S. § 5020-303